Photocurable compositions

ABSTRACT

Novel photocurable compositions employing the addition of thiols to polymers having terminal vinyl-acetal functions, products prepared therefrom, and process for preparation thereof are disclosed. The cured products are films useful in coating floor tile, fabrics, and wooden articles.

This is a divisional of application Ser. No. 720,531 filed Sept. 7,l976.

BACKGROUND OF THE INVENTION

This invention relates to the art of "thiol-ene" cures of polymers, thatis cure of polymers by radiation induced addition of thiol functions tocarbon-carbon unsaturation.

The basic principles of radiation induced thiol addition tocarbon-carbon unsaturation, particularly terminal unsaturated bonds, invarious molecules are reviewed by Griesbaum in Angewandte Chemie(International Edition), 9, (1970), page 273.

The use of this type of reaction in curing various polymers, includingurethane polymers, to form elastomers and resins is well-known in theart. No polymers having vinyl-acetal terminal groups are known to havebeen cured using this method.

SUMMARY OF THE INVENTION

The invention provides a photocurabie composition which comprises apolythiol and a polyene derived from a vinyl-acetal.

The tangible embodiments of this composition aspect of the inventionpossess the inherent applied use characteristic of being curable totough flexible films useful as coatings for floor tile, fabrics, andwood.

A preferred embodiment of this composition aspect resides in the conceptof a photocurable composition as defined hereinabove wherein the polyeneis derived from vinyl-1,3-dioxolane, or vinyl-1,3-dioxane.

Another preferred embodiment resides in the concept of a photocurablecomposition as defined hereinabove wherein the polythiol is selectedfrom a compound of the formula Q--SH)_(m) wherein m is at least 2 and Qis an m valent radical derived by removal of hydrogen from terminal orring positions of straight, branched chain, or cyclic alkyl of from 2 to20 carbon atoms, benzene, straight or branched chain alkyl-phenyl,biphenyl, phenyl-straight, branched chain, or cyclic alkylene-phenyldiphenyl-ether, straight, branched chain, or cyclic alkyl-phenyl ether,di-straight, branched chain, or cyclic alkyl ether,polyphenylene-polyether, polyphenylene-polyalkylene-polyether,polyalkylene polyether, polyester, or esters of polyols.

Still another preferred embodiment of this composition aspect of theinvention resides in the concept of a photocurable composition ashereinabove defined wherin the polyene is a compound of the formula:##STR1## wherein Q' is an a-valent residue derived from a hydroxylterminated polyester, polyether, polyamide, polyester polyether, orpolyester-polyamide by removal of hydrogen from the hydroxyl functions;X is a divalent alkylene, or arylene linking group; Y is a covalent bondor an alkylene group of from 1 to 20 carbon atoms; R is hydrogen, alkylof 1 to 20 carbon atoms, or haloalkyl of 1 to 20 carbon atoms; R' ishydrogen, alkyl of 1 to 20 carbon atoms, haloalkyl of 1 to 20 carbonatoms, fluoro, or chloro; n is 0 or 1 and a is a positive number greaterthan 1.

The invention also provides a film suitable for coating a substratewhich comprises a cured film formed by treating with actinic radiation alamina comprising a polythiol and a polyene derived from a vinyl acetal.

The invention further provides an article of manufacture consisting of asubstrate coated on at least one surface with a film derived by treatinga lamina coated on said surface with actinic radiation, said laminacomprising a polythiol and a polyene derived from a vinyl acetal.

The invention still further provides a method for the preparation of anarticle of manufacture coated on at least one surface with a cured filmderived from a polythiol and a polyene derived from a vinyl acetal whichcomprises applying to at least one surface of a substrate a laminacomprising a polythiol and a polyene derived from a vinyl acetal: andtreating said lamina with actinic radiation.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In describing the preparation of the compositions of the invention,reference will first be made to the method of synthesis of a specificembodiment of the polyenes derived from a vinyl acetal, namely a5-ethyl-5-hydroxy methyl-2-vinyl-m-dioxaneterminated-toluene-diisocyanate capped hydroxy terminated polyethyleneadipate having approximately 800 equivalent weight of the polyester andan NCO content of approximately 3.0% before the terminal group wasintroduced (I).

5-ethyl-5-hydroxy methyl-2-vinyl-m-dioxane (II) a starting material forthe preparation of I may be prepared from trimethylol propane andacrolein in a reaction analogous to that described in U.S. Pat. No.3,010,923 for the reaction of α, β, ω-triols with acrolein for thepreparation of vinyl-1,3-dioxolanes.

Treatment of II with an approximately 800 equivalent weight hydroxylterminated polyethylene adipate polyester capped with toluenediisocyanate to an NCO content of 3.0% at elevated temperature,conveniently 90° C., for a moderate reaction period, conveniently 9-10hours, gives I.

To prepare a specific embodiment of the compositions of the invention,I, pentaerythritol tetrakis mercapto acetate, a U.V. initiator,conveniently benzophenone, an anti-oxidant, conveniently2,6-di-tertiary-butyl-4-methyl-phenol, and, if desired, a flow controlagent such as Union Carbide Corporation's UCC L-7602 are blended.

A suitable volatile solvent in sufficient proportion to adjust viscosityfor convenient application may be added. Methyl ethyl ketone is aconvenient solvent for this purpose.

The blended material is applied in a thin layer or lamina to thesubstrate to which it is desired to apply the coating and any solventwhich may be present allowed to evaporate. The cast uncured film laminais then exposed to U.V. radiation and cured.

One skilled in the art will recognize that in addition to the specificintermediate II illustrated hereinabove, it is possible to treatacrolein or acrolein substituted in the β position with hydrogen, alkyl,halo alkyl, fluoro or chloro with an α, β, ω-triol such as glycerol,1,2,6-hexanetriol and the like, or an α, γ, ω-triol such as1,3,6-hexanetriol and the like in addition to the trimethylol propaneillustrated or such triols substituted in the β or γ position withalkyl, or halo alkyl to obtain the vinyl-m-dioxane orvinyl-1,3-dioxolane derivatives contemplated as suitable for use in theinvention. Thus any 1,2,(3 or higher) or 1,3,(5 or higher)triol will besuitable.

Similarly it will be readily apparent to one skilled in the art that anyhydroxy terminated polyester, polyether or polyamide may be substitutedfor the polymeric polyethylene adipate illustrated as a suitableprepolymer starting material.

Illustrative of suitable prepolymers will be those liquid polyestersderived from such polyhydric alcohols as: ethylene glycol,1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol,2,3-butanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol,2,3-pentanediol, 2,4-pentanediol, 1,6-hexanediol, 1,5-hexanediol,1,4-hexanediol, 1,3-hexanediol, 2,3-hexanediol, 2,4-hexanediol,2,5-hexanediol, 1,7-heptanediol, 1,5-heptanediol, 3,5-heptanediol,1,10-decanediol, para-xylene glycol, the bis-(β-hydroxyethylether) ofhydroquinone, neopentylglycol, glycerin, pentaerythritol,trimethylolpropane, triethylolethane and the like and polycarboxylicacids such as, for example, adipic acid, oxalic acid, succinic acid,methyl adipic acid, sebacic acid, glutaric acid, pimelic acid, azelaicacid, suberic acid, phthalic acid, terephthalic acid, isophthalic acid,1,2,4-benzene tricarboxylic acid, maleic acid, fumaric acid, itaconicacid, citraconic acid and the like, liquid polyamides derived from thereaction between polycarboxylic acids as illustrated hereinabove andpolyamines such as, for example, ethylene diamine, propylene diamine,butylene diamine, pentamethylene diamine, hexamethylene diamine,phenylene diamine, tolylene diamine, xylylene diamine,4,4'-diamino-diphenylmethane, cyclohexylene diamine, naphthylenediamine, and the like, or liquid polyester polyamides frompolycarboxylic acids and amino alcohols such as amino ethanol, aminopropanol, amino butanol, and the like, also polyesters prepared fromlactones such as caprolactone and the like, polyhydric polyalkyleneethers such as, for example, the condensation products of an alkyleneoxide such as ethylene oxide, propylene oxide, butylene oxide, amyleneoxide and the like with a suitable initiator such as water or any of thepolyalcohols, polyamines, or amino alcohols set forth herein.

In addition to the toluene diisocyanate illustrated hereinabove it willbe obvious that the above hydroxy terminated prepolymer may be endcapped with other diisocyanates as a connecting link with thehydroxy-vinyl-m-dioxanes or hydroxy-vinyl-1,3-dioxolanes. Illustrativeof these are, for example, 1-methoxyphenyl-2,4-diisocyanate,1-methyl-4-methoxyphenyl-2,5-diisocyanate.1-ethoxyphenyl-2,4-diisocyanate, 1,3-dimethoxyphenyl-4,6-diisocyanate,1,4-dimethoxyphenyl-2,5-diisocyanate, 1-propoxyphenyl-2,4-diisocyanate,1-isobutyoxy-2,4-diisocyanate, 1,4-diethoxyphenyl-2,5-diisocyanate,diphenylether-2,4-diisocyanate, naphthalene-1,4-diisocyanate,1,1'-dinaphthalene-2,2'-diisocyanate, biphenyl-2,4-diisocyanate,3,3'-dimethylbiphenyl-4,4'-diisocyanate,3,3'-dimethoxybiphenyl-4,4'-diisocyanate,diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate,diphenylmethane-2,2'-diisocyanate, 3,3'-dimethoxydiphenylmethane-4,4'-diisocyanate, benzophenone-3,3'-diisocyanate,ethylene diisocyanate, propylene diisocyanate, butylene diisocyanate,pentylene diisocyanate, methylbutylene diisocyanate, tetramethylenediisocyanate, pentamethylene diisocyanate, hexanethylene diisocyanate,dipropyl diisocyanate ether, heptanethylene diisocyanate,2,2-dimethylpentylene diisocyanate, 3-methoxy-hexamethylenediisocyanate, octamethylene diisocyanate, 2,2,4-trimethylpentylenediisocyanate, 3-butoxyhexamethylene diisocyanate, 1,3-dimethylbenzenediisocyanate, 1,4-dimethylbenzene diisocyanate, 1,2-dimethylcyclohexanediisocyanate, 1,4-dimethylcyclohexane diisocyanate, 1,4-diethylbenzenediisocyanate, 1,4-dimethylnaphthalene diisocyanate,1,5-dimethylnaphthalene diisocyanate, cyclohexane-1,3-diisocyanate,cyclohexane-1,4 diisocyanate, 1-methylcyclohexane-2,4-diisocyanate,1-methylcyclohexane,-2,2-diisocyanate,1-ethylcyclohexane-2,4-diisocyanate,dicyclohexylmethane-4,4'-diisocyanate,dicyclohexylmethylmethane-4,4'-diisocyanate,dicyclohexyldimethylmethane-4,4'-diisocyanate,2,2-dimethyldicyclohexylmethane-4,4'-diisocyanate,3,3',5,5'-tetramethyldicyclohexylmethane-4,4'-diisocyanate,4,4'-methylene-bis(cyclohexylisocyanate), ethylidene diisocyanate,4,4'-diphenyl diisocyanate, dianisidine diisocyanate, 1,5-naphthalenediisocyanate, m-phenylene diisocyanate, isopropylidene bis(phenyl orcyclohexyl isocyanate), 1,3-cyclopentylene diisocyanate,1,2-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate,4,4',4"-triphenylmethane triisocyanate, 1,3,5-triisocyanate benzene,phenylethylene diisocyanate, and the like.

It will in addition be obvious that the polythiol component of thecomposition of the invention, in addition to thepentaerythritol-tetrakis-mercaptoacetate illustrated, may be thiolanalogs of any of the aforementioned polyhydroxy compounds or of theaforementioned polyhydric polyethers, polyesters, or polyamides, orpolyesteramides or the ester produced by reaction of these polyalcoholswith a thiol substituted carboxylic acid. Illustrative of thesecompounds are ethane dithiol, propane dithiol, 1,1'-dimercaptodiethylether, bis-(2-mercaptoethyl)-formal,ethylene glycol dimercaptopropionateand the like.

As stated above the compositions of the invention contemplate theoptional inclusion, in addition to the aforementioned vinyl acetal andpoly thiol components, of various standard additives well-known to theart for the purposes of viscosity control, case of processing, storagestability and the like. No one or combination of these is particularlyessential to making or using the invention, the only real limitationbeing that they be materials which one skilled in the art would expectto not interfere with the radiation cure by preferentially absorbing orinterfering with the penetration of the curing radiation into theuncured composition.

Typical additives will include volatile solvents such as acetone,methylethyl ketone, methanol, ethanol and the like, anti-oxidants,actinic radiation cure initiators such as benzophenones, benzoins andothers known in the art, flow control agents such as the organicsilicones, reactive diluents for viscosity lowering to provide greaterease in film spreading such asdi-(5-ethyl-5-hydroxymethyl-2-vinyl-m-dioxane)-adipate and the like.

The following Examples further illustrate the best mode contemplated bythe inventors for the practice of their invention.

EXAMPLE 1 5-Ethyl-5-Hydroxymethyl-2-Vinyl-m-Dioxane

Following a procedure analogous to that disclosed and referenced byIkeda in U.S. Pat. No. 3,010,923 there is obtained from trimethylolpropane and acrolein the title product in 80% yield, B. Pt. (1.75-2.7mm) 100°-108° C., n_(D) ²⁵ 1.4710

Analysis For: C₉ H₁₆ O₃ : Calculated C, 62.77; H, 9.36; OH No., 325.7.Found C, 62.17; H, 10.40; OH No., 316.3 (Corr.). Acid No. (Found) 0.15.

EXAMPLE 2 4-Hydroxymethyl-2-Vinyl-1,3-Dioxolane and5-Hydroxy-2-Vinyl-m-Dioxane

Following a procedure analogous to that referenced in Example 1 there isobtained the title products as a mixture in 62% yield, B. Pt. (13-11 mm)100°-106° C.

Analysis For: C₆ H₁₀ O₃ : Calculated: C, 55.37; H, 7.75; OH No. 431.1.Found: C, 55.46; H, 6.88; OH No. 423.7 (Corr.). Acid No. (Found) 0.12.

EXAMPLE 3 Toluene Diisocyanate Terminated Polyethylene Adipate EndCapped With 5-Ethyl-5-Hydroxymethyl-2-Vinyl-m-Dioxane

A hydroxyl terminated polyethylene adipate having an initial molecularweight of 800 was treated with toluene diisocyanate to an NCO content of2.91%. This compound was treated with the product of Example 1 at anOH/NCO ratio of 1.05 for 9.5 hours at 90° C., in the presence of 0.02%phenothiazine as a polymerization inhibitor. The final NCO content was0.53%.

Unsaturation: (Equivalents/100 g) (By ICI titration, 2 equivalents equalto 1 mole >C═C<)

Calculated: 0.13. Found: 0.145.

EXAMPLE 4 Toluene Diisocyanate Terminated Polyester End Capped With aMixture of 4-Hydroxymethyl-2-Vinyl-1,3-Dioxolane and5-Hydroxy-2-Vinyl-m-Dioxane

Following a procedure analogous to that of Example 3 treat the toluenediisocyanate terminated polyethylene adipate polyester prepared in thatExample with the product of Example 2 for 6.5 hours at 90° C. to givethe title product. The final NCO content was 0.31%.

Unsaturation: (ICl titration, equiv./100 g)

Calculated: 0.125. Found: 0.145.

EXAMPLE 5 Formulations of Vinyl Acetal End Capped Polyesters andPolythiols and Polymers Thereof

Formulations of the vinyl acetal end capped product of Example 3 andpolythiols were prepared as follows:

    ______________________________________                                                             Formulation:                                                                  (Parts by Weight)                                        Ingredient             A        B                                             ______________________________________                                        Vinyl acetal end capped polyester                                                                    85       86.2                                          Methyl ethyl ketone    62       62                                            2,6-di-t-butyl-4 methyl-phenol                                                                       0.050    0.050                                         Pentaerithrytol tetrakis (mercapto acetate)                                                          7        3.5                                           CH.sub.2 (OCH.sub.2 CH.sub.2 SH).sub.2                                                               --       3.0                                           Benzophenone           1.5      1.5                                           UCC L-7602             1        1                                             (Union Carbide Corp.-Organo.                                                  Silicone)                                                                     ______________________________________                                    

Films of the above formulations were cast as a methyl ethyl ketonesolution and air dried prior to cure. After cure, film thickness was 4mil. Curing was 2 passes at 20 feet per minute using a QC 1202 ANProcessor (PPG Industries Inc., Radiation Polymer Co.) under two 12 in.lamps having a linear power density of 200 watts per inch. Thesecompositions also cured slowly on exposure to air.

Properties obtained after U.V. cure as above are:

    ______________________________________                                                       A         B                                                    ______________________________________                                        Elongation (%)   470         410                                              Tensile Strength (psi)                                                                         1470        150                                              Modulus (psi)                                                                 100%             90          45                                               200%             165         65                                               300%             300         100                                              400%             500         --                                               ______________________________________                                    

The subject matter which applicants regard as their invention isparticularly pointed out and distinctly claimed as follows:
 1. Aphotocurable composition which comprises a polythiol and a polyenederived from a vinyl acetal.
 2. A composition as defined in claim 1wherein the vinyl acetal is a vinyl-1,3-dioxane or avinyl-1,3-dioxolane.
 3. A composition as defined in claim 2 wherein thepolythiol is selected from a compound of the formula: Q--SH)_(m) whereinm is at least 2 and Q is an m valent radical derived by removal ofhydrogen from terminal or ring positions of straight, branched chain, orcyclic alkyl of from 2 to 20 carbon atoms, straight or branched chainalkyl-phenyl, diphenyl, phenyl- straight or branched chainalkylene-phenyl, diphenyl ether, straight, branched chain, or cyclicalkyl-phenyl ether, di-straight or branched chain, or straight orbranched chain alkyl substituted cyclic alkylether,polyphenylene-polyether, polyphenylene-polyalkylene polyether,polyalkylene polyether, polyester, or ester of a polyol.
 4. Acomposition as defined in claim 3 wherein the polyene is a compound ofthe formula: ##STR2## wherein Q' is an a valent residue derived from ahydroxyl terminated polyester, polyether, polyamide,polyester-polyether, or polyester-polyamide by removed of hydrogen fromthe hydroxyl functions; X is a divalent alkylene or arylene linkinggroup; Y is a covalent bond or an alkylene group of 1-20 carbon atoms; Ris hydrogen, alkyl of 1 to 20 carbon atoms, or haloalkyl of 1 to 20carbon atoms; R' is hydrogen, alkyl of 1 to 20 carbon atoms, haloalkylof 1 to 20 carbon atoms, fluoro or chloro; n is 0 or 1 and a is apositive number greater than
 1. 5. A composition as defined in claim 4wherein Q' is derived from a hydroxyl terminated polyester.
 6. Acomposition as defined in claim 4 wherein the polythiol is a thiolterminated polyester, polyether, dialkyl formal, or ester of a polyol.7. A composition as defined in claim 5 wherein the polythiol is a thiolterminated polyester, polyether, dialkyl formal, or ester of a polyol.8. A composition as defined in claim 7 wherein the thiol terminatedester of a polyl is pentaerythritol tetrakis mercaptoacetate.
 9. Acomposition as defined in claim 7 wherein the thiol terminated dialkyformal is bis-(2-mercaptoethyl)-formal.